BRT vs. Traffic Lane

Back of the envelope calculation here:

For a BRT:

Assuming an articulated bus is purchased, passenger capacity per bus can be estimated at 90 passengers for an articulated New Flyer vehicle[2], or 108 for an Xcelsior vehicle. With 5 minute peak headways, this equates to 12 buses per hour per direction, or 24 buses/hour total. With a potential of 90 passengers per bus, the Provo-Orem BRT would have a capacity of (90*60/5*2) is 1080 passengers per direction per hour. For the Xcelsior, the Provo-Orem BRT would have a capacity of (108*60/5*2) is 1296 passengers per direction per hour. The IRIS Civic Bus, used for the Las Vegas MAX, has a capacity of 120 persons; peak hour capacity in which case would be 1440 passengers per direction per hour.  

So how does that compare to a highway? 

---

Max capacity per lane for automobiles is 1900 per hour, says "Mike on Traffic'. Table 31 of the "Default Values for Highway Capacity and Level of Service Analyses" suggests this is a reasonable number.

So the BRT (at max capacity) is less than that for freeway lane. Damning, eh? Not quite. That's BRT capacity at 5 minute headways, or 12 buses per hour. BRT is suggested to cap out at 17,000 per hour.

But I'm skeptical. How good a source is Marin? Assuming 17,000 is both directions, with a capacity of 120 per bus, that's 71 buses per hour. That's a bus every 50 seconds. That strikes me as unrealistic.

Ontario suggests a somewhat lower number, more like 5k (bus in bus lane), in one hour, in one direction. So that's more like 10,000 in both directions, rather than 17,000. 5,000 passengers per hour at 120 passengers per hour is about 42 buses per hour, which is a bus about every minute and 45 seconds. That seems more feasible.

But we are talking about Provo here, so let's ignore the 'theoretical max' and talk about the specifics. Assume the midpoint (the Xcelsior at 108 passengers) rather than the CivicBus at 120.

For the Xcelsior, the Provo-Orem BRT would have a capacity of (108*60/5) is 1296 passengers per direction per hour. If we increase that to a bus every 4 minutes, we get 15 buses per hour, with a max capacity of 1620 persons per direction per hour (peak capacity). Following that logic, we can generate the following chart:

Headway------- Buses per hour-----------Capacity

        5 min                     12                              1296

        4 min                     15                              1620

       3:30 min                 17                              1836

       3:20 min                 18                              1944

        3 min                     20                              2160

        2 min                     30                              3240

So a BRT carries about the same at 17-18 buses per hour. 

Does that mean we shouldn't build BRT when the capacity would be lower? 

No. 

It means that BRT scales better than a general traffic lane. From the examples above, it's pretty clear that a bus every two minutes is feasible. Which means that a dedicated lane of BRT has a capacity of over 3000 persons per direction per hour, or about half again what a general traffic lane is.

Now, the really big, really nice BRT systems don't just have one BRT lane: They have two. Some have four (for local and express). Those are the places that really have a 'surface subway'. The capacity that arrangement provides must be huge. 

Light Rail

Wikipedia says LRT has a capacity of 220 per car. Assuming the calculations above apply, that gives us something like: 

Headway------- Traincars per hour-----------Capacity

       20 min                     3                                660  

       15 min                     4                                880

        5 min                     12                              2640

(I have serious doubts of UTA's ability to run a train more than once every 5 minutes...the system just is not designed for it)

But that's with only a single car per train. If they couple cars into trainsets (and SLC's long blocks permit up to four cars per trainset), the max theoretical capacity is quadrupled. 

Headway------- Traincars per hour-----------Capacity

       20 min                     3                                2640  

       15 min                     4                                3520

        5 min                     12                              10,560

Those are crazy numbers. That means on game days at the U (when every train is packed, and UTA is running trains every 5 minutes) TRAX is carrying about 5.5 freeway lanes worth of people.

Can you imagine the mess on I-15 without it?

[1] http://www.metro-magazine.com/bus/news/719169/utah-transit-to-add-35-more-60-foot-new-flyer-xcelsiors

[2] https://www.nbrti.org/docs/pdf/EmX_%20Evaluation_09_508.pdf

Bus vs. Rail

I am going to punch the next feckless moron to conflate the costs of mixed-traffic bus system with a dedicated running-way rail system. It's simply not an apples to apples comparison, in either cost or quality of service. One is a Buick, and the other is a Cadillac. While both enjoy the same potential ridership (in terms of the built environment), there is a vast difference in performance. To call out one aspect in particular: system delay. As the Transit Capacity and Quality of Service Manual is good enough to point out:

This point of view also includes measures of
facility capacity in terms of the numbers of transit vehicles or total vehicles that can
be accommodated. Because transit vehicles carry passengers, these measures also
reflect the passenger point of view: passengers on board a transit vehicle traveling at
an average speed of 12 mph (20 km/h) individually experience this same average
travel speed. However, because these vehicle-oriented measures do not take
passenger loading into account, the passenger point of view is hidden, as all vehicles
are treated equally, regardless of the number of passengers in each vehicle. For
example, while a single-occupant vehicle and a 40-passenger bus traveling on the
same street may experience the same amount of delay due to on-street congestion
and traffic signal delays, the person-delay experienced by the bus is 40 times as great
as the single-occupant vehicle.

It's not a question of bus versus rail, (as many BRT projects are empirically proving) but a matter of right of way. Dedicated running-way provides value, but at a price. Whether the value is worth the price depends on the project, not the technology. 

Bus vs. Trains

I was reading Human Transit today, and thinking about the rail map. SLC has a similarly complex bus system. Why is not possible to have a similar map? Jared Walker has the right of it when he says 'many transit services that are stuck in mixed traffic'. This is the fundamental divide--not bus vs. train, but dedicated right of way vs. mixed traffic. Trains, being heavier and slower to stop, frequently get their own. Buses do not, and that makes all the difference.  Effective BRT means dedicated right of way

Old Greek Town Station needs to go

Currently, SLC has a problem: It's kind of an open secret that the TRAX ridership between the Arena Station and the Salt Lake Central Station kind of sucks. And I think I know why: Old Greek Town station is FAR too close to both Salt Lake Central Station and Planetarium Station. Salt Lake's blocks may be 660' long, but stop spacing for transit should be about 1200', and the station is within 1000' of both. I know WHY it's there--SLC's former Mayor, Rocky Anderson, demanded it as a nexus for additional 'Transit Oriented Development' in downtown. It was a bad idea at the time, but UTA permitted it because Salt Lake City was paying for the line. 

Along the Sandy line, each additional TRAX stop adds about 3 minutes to the journey. Downtown, I'd estimate it's greater. The Sandy line has dedicated Right of Way, and so never needs to deal with traffic lights. Downtown, making the stop at Greek town means the train has to match up with the traffic light. When it fails to do so, that requires waiting for the light to cycle, adding another minutes worth of wait time. 

Adding the 9400 South TRAX station cost about $2.1, so closing a station represents a pretty blatant waste of funds, plus the additional political cost of confusion by riders attempting to board or disembark at a non-functional station.